Lifjeld Jan T, Dunn Peter O, Whittingham Linda A
Zoological Museum, University of Oslo, P.O. Box 1172 Blindern, 0318, Oslo, Norway.
Department of Biological Sciences, University of Wisconsin-Milwaukee, P.O. Box 413, 53201, Milwaukee, WI, USA.
Oecologia. 2002 Jan;130(2):185-190. doi: 10.1007/s004420100798. Epub 2002 Jan 1.
We examined cellular immunity of adult tree swallows feeding nestlings under variable weather conditions. Birds received an injection of phytohaemagglutinin (PHA), which causes a local swelling, reflecting the strength of T-cell-mediated immunocompetence. There was a negative relationship between the immune response and the number of nestlings in the brood (range 3-6 young) which suggests that parental effort suppresses the immune function. However, there was also a strong effect of ambient temperature and food abundance (aerial insects) on immune response. Parents that received the PHA injection during cold weather and at low food abundance showed a suppressed immune response compared to birds treated during more favourable conditions. They also lost more body mass during the 24 h inoculation period, and their offspring showed reduced growth. When controlling for ambient temperature and food abundance in a multivariate analysis, there was no longer any significant effect of brood size on the parents' immune response. Three of 39 pairs deserted their broods after PHA injection. All three desertions took place when the mean ambient temperature fell below 13°C. The PHA response is known to have both heritable and environmental components; our study emphasizes its condition-dependency. Previous studies of other passerine birds have shown that high levels of parental effort may have an immunosuppressive effect. Our study indicates that weather conditions may override the effects of natural variation in parental effort, and that the PHA response is particularly influenced by short-term fluctuations in energy balance.
我们研究了成年树燕在不同天气条件下喂养雏鸟时的细胞免疫情况。给鸟类注射植物血凝素（PHA），它会引起局部肿胀，反映T细胞介导的免疫能力的强弱。免疫反应与一窝雏鸟的数量（范围为3至6只幼鸟）之间呈负相关，这表明亲代投入会抑制免疫功能。然而，环境温度和食物丰富度（空中昆虫）对免疫反应也有很强的影响。与在更有利条件下接受PHA注射的鸟类相比，在寒冷天气和食物丰富度较低时接受PHA注射的亲鸟免疫反应受到抑制。在接种后的24小时内，它们体重减轻得更多，其后代的生长也受到抑制。在多变量分析中控制环境温度和食物丰富度后，窝雏数量对亲代免疫反应不再有任何显著影响。39对亲鸟中有3对在注射PHA后弃巢。所有三次弃巢都发生在平均环境温度降至13°C以下时。已知PHA反应具有遗传和环境成分；我们的研究强调了其对条件的依赖性。先前对其他雀形目鸟类的研究表明高水平的亲代投入可能具有免疫抑制作用。我们 的研究表明天气条件可能会掩盖亲代投入自然变化的影响，并且PHA反应特别受能量平衡短期波动的影响。
